Chip- and abrasion-resistant polyurethane coating composition having improved adhesion

Abstract

The invention is a coating composition which includes fully reacted, solvent-soluble polyurethane, an adhesion-promoting amount of vinyl chloride-vinyl ester copolymer, and a solvent for the polyurethane and the copolymer to make the composition coatable. A method of coating is also provided comprising applying to a surface the coating composition and permitting the coating composition to dry. The invention further provides a surface coated with the dry coating composition.

I claim: 
     
       1. A composition capable upon drying by solvent evaporation of providing a clear chip- and abrasion-resistant coating having improved adhesion to acrylic surfaces, said composition comprising: (a) fully reacted solvent-soluble polyurethane derived from an aliphatic diisocyanate;   (b) an adhesion-promoting amount of vinyl chloride-vinyl ester copolymer; and   (c) solvent for said polyurethane and said copolymer to make said composition coatable wherein said adhesion-promoting amount of said vinyl chloride-vinyl ester copolymer comprises from about 5 to about 30 parts by weight based on 100 parts of the composition on a dry solvent-free basis.     
     
     
       2. The composition of claim 1 wherein said vinyl chloride-vinyl ester copolymer is modified by the addition of about 1 to 2% maleic acid comonomer. 
     
     
       3. The composition of claim 1 wherein said vinyl chloride-vinyl ester copolymer is vinyl chloride-vinyl acetate copolymer. 
     
     
       4. The composition of claim 1 having a Brookfield viscosity of about 50-500 cps employing a No. 2 spindle at 20 rpm and 25° C. 
     
     
       5. The composition of claim 1 wherein said fully reacted solvent-soluble polyurethane has a weight average molecular weight of about 18,000-50,000. 
     
     
       6. The composition of claim 1 wherein said solvent is a blend of an alcohol having from 1-6 carbon atoms and an ester having from 1-6 carbon atoms. 
     
     
       7. The composition of claim 1 wherein said vinyl chloride-vinyl acetate copolymer comprises about 60-90 mole % vinyl chloride and 10-40 mole % vinyl ester. 
     
     
       8. An acrylic surface coated with a clear coating comprising fully reacted, solvent-soluble aliphatic polyurethane and an adhesion-promoting amount of vinyl chloride-vinyl ester copolymer wherein said adhesion-promoting amount of said vinyl chloride-vinyl ester copolymer comprises from about 5 to about 30 parts by weight based on 100 parts of the composition on a dry solvent-free basis. 
     
     
       9. The surface of claim 8 wherein said vinyl chloride-vinyl ester copolymer is carboxyl-modified vinyl chloride-vinyl acetate copolymer.